LCD Pixel Circuit with Segmented Switching for Gray Inversion
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Solution Overview
Problem
Liquid crystal displays (LCDs) suffer from poor viewing angle and visibility due to their viewing direction dependency, leading to gray inversion and limited lateral visibility, which is exacerbated by their use in multimedia devices requiring wide-angle viewing of pictures and motion pictures.
Innovation Solution
The implementation of a liquid crystal display with a liquid crystal capacitor, a first switching element, a second switching element, and a transformation capacitor, where the difference in their activation times is greater than one horizontal period but less than one frame period, allowing for a capacitance ratio that enhances side visibility and motion picture display characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional liquid crystal display with single switching element is used, then the device complexity is low, but the viewing angle and visibility are poor due to gray inversion
Solution Approach 1:
The pixel circuit is divided into two separate switching elements (first switching element and second switching element) that operate at different time intervals. The first switching element transmits data voltage during the first time period, while the second switching element transmits compensation voltage during the second time period. This segmentation allows independent optimization of data writing and compensation functions, resolving the gray inversion problem while maintaining manageable circuit complexity.
Solution Approach 2:
The patent implements periodic switching actions where the first and second switching elements are turned on alternately during different time periods within each frame cycle. The first switching element operates during the first time period, and the second switching element operates during the second time period, creating a periodic pattern that effectively compensates for viewing angle dependencies and eliminates gray inversion.
2Reliability
If the switching elements are activated simultaneously, then the circuit control is simple, but the luminance compensation for side visibility is insufficient
Solution Approach 1:
The patent implements periodic switching actions where the first and second switching elements are turned on alternately during different time periods within each frame cycle. The first switching element operates during the first time period, and the second switching element operates during the second time period, creating a periodic pattern that effectively compensates for viewing angle dependencies and eliminates gray inversion.
Solution Approach 2:
The first switching element is activated during the first time period to establish the initial data voltage in the liquid crystal capacitor. Subsequently, the second switching element is activated during the second time period to apply compensation voltage that corrects for viewing angle effects. This preliminary action sequence ensures proper luminance compensation for side visibility while maintaining clear control timing.
3Reliability
If a single capacitance configuration is used, then the circuit is simple, but the motion picture display characteristics are poor
Solution Approach 1:
The capacitance function is segmented into two distinct capacitors: the liquid crystal capacitor that stores data voltage and the transformation capacitor that provides compensation voltage. This segmentation allows the transformation capacitor to be specifically optimized for motion picture display characteristics, improving reliability while keeping the overall circuit configuration manageable through clear functional separation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration significantly improves viewing angle and visibility by ensuring high and low luminances are alternately represented during one frame, resulting in improved side visibility and motion picture display characteristics, reducing gray inversion and maintaining contrast ratio.
Implementation Method 1
voltages are applied to the field generating electrodes to generate an electric field in the liquid crystal layer, and an alignment of liquid crystal molecules in the liquid crystal layer is determined by the electric field
Implementation Method 2
a polarization of light incident to the liquid crystal layer is controlled to display an image on the liquid crystal display
Implementation Method 3
due to refractive anisotropy, the LCD has a disadvantage of a viewing direction dependency
Implementation Method 4
a liquid crystal capacitor; a first switching element that transmits a data voltage to the liquid crystal capacitor
Data Source
AI summary
A liquid crystal display includes: a liquid crystal capacitor; a first switching element which transmits a data voltage to the liquid crystal capacitor; a second switching element connected to the liquid crystal capacitor; and a transformation capacitor connected to the second switching element. A difference between a first time when the first switching element is turned on and a second time when the second switching element starts is turned on is greater than 1 horizontal period and less than 1 frame period.